Process of producing aluminium.



-PATENTED FEB. 3, 190MB.

H. F. D.` SCHWAHN. l

-PROGESS 0F PRODUCIN G ALUMINIUM.

APPLICATION FILED APB.. 9. 1900.

N0 MODEL. v

Zvw/vrai( A4713?, Ml

' UNITED STATES PATENT OFFICE.

HEINRICHl F. D. SCHWAHN, OF ST. LOUIS, MISSOURI.

PROCESS OF PRODUCING ALUMINIUM.

SPECIFICATION forming part of Letters Patent No. 719,698, dated February3, 1903.

Application led April 9, 1900. Serial No. 12,150. (No specimens.)

To all whom, t may concern:

Be it known that I, HEINRICH F. D. SCHWAHN, a citizen of the UnitedStates, and a resident of the city of St. Louis, in the State ofMissouri, have invented a new and useful Process of Producing Aluminium,of which the following description is so full, clear, and

exact as to enable those skilled in the art to which it appertains touse the same.

The object of my present invention is to provide a practical method forproducing aluminium which shall admit of the production of the metalwith an economy not heretofore possible. v

My invention consists in subjecting certain aluminium compounds, ofwhich aluminium sulfate may be taken as a type, to heat in the presenceof a reducing agent containing sulfur, as hereinafter specified. Theoperation is conducted within a substantially closed retort, whereby theatmosphere may be excluded and a slight pressure of reducing-gasesmaintained.

As raw material for reduction to aluminium I preferably employ hydrousaluminium sulfate Al2(SO,)3-{1GH2O, but may substitute therefor theoXid, sulfid, or other compound. If the hydrous sulfate be used, it ispreferably preliminarily calcined at a moderate temperature, whereby itloses its water of crystallization and is converted into a light porousmass readily permeable by gases.

As a reducing agent I may employ a hydrocarbon gas, of which naturalgas, the gases derived from the decomposition of carbide, thoseresulting from the treatment of crude` coal-oil or from the distillationof soft coal may be taken as types, aV mixture of such gases, water-gas,producer-gas, or carbon monoxid. Preferably, however, I employ the afterspecified,no further treatment is necessary; otherwiseI add a definiteproportion,

preferably about live per cent., of a sulfurbearing compound, as carbondisuld.

Instead of treating the aluminium compound by a reducing-gas, as abovespecified, I may mix with said aluminium compounda carbonaceous reducingagent, as a soft coal of high sulfur content, which is capable ofyielding such gas in contact with the aluminium compound and at asucient temperature of eecting the reduction to metal.

My invention consists then in'reducing an aluminium compound, preferablythe porous sulfate, by a reducing agent, of which sulfur is a component.

For a clear understanding of the invention reference is made to theaccompanying drawing, wherein a retort R of graphite, such as iscommonly employed for the production of crucible, is shown supported inan upright position within the walls A in such manner as to provideencircling lines for the heated gases proceeding from thehydrocarbonburner G and introduced through the chamber C. F representsan yescape-flue for the waste gases. Within the retort and in its lowerportion a support P is provided for the charge, apertured, as at p2, forthe admission to the charge ot' the reducing-gas. The gases derived fromthe reaction, together with such excessof reducing-gas as may bepresent, escape through the flue E, shown as provided with a valve ordamper F2.

The charging-openingis preferably in th cover of the retort and isprovided witha suitable closure O. Beneath the support P is theI chamberS, into which the reducinggas is introduced. A tap-hole T and plug B areprovided for the withdrawal of the reduced metal, which is conducted bythe usual runway to the collecting vessel j. Into this chamber S isintroduced a pipe P', provided with a regulating-valve, as shown at F',and serving for the introduction of a reducing agent of the characterhereinbefore speciiied.

I will now describe the operation of producing aluminium, taking for thepurpose of illustration the production of the metal from i the hydratedsulfate by means of heat, a hydrocarbon gas, and a sulfur compound. As asulfur compound I will take carbon disulfid as an example.

The hydrous sulfate is mixed with a certain small proportion of asuitable tl ux, preferably a compound of an alkali metal, as sodiumchlord. The advantage possessed by a ux of this character is that itfacilitates the reaction without contaminating the aluminium.

The hydrous sulfate and flux are calcined at a. moderate temperature ina reverberatory furnace, broken into pieces about the size of a walnut,and charged', as shown at a', into the interior U of the retort. Thelatter is then brought to a sufficient temperature, which need notexceed a bright red heat or, say, 800 to 900 centigrade by means of theburner G, and the reducing-gas consisting of a hydrocarbon containingaboutfve per cent. of carbon disuld is introduced through the pipe P'.Owing to the porous or multicellular character of the charge, every partthereof is subjected to the action of` the reducing-gases, and thereducedV metal flows through the apertures p2 and collects, as shown atD, in the lower portion of the chamber S. Preferably the reducing-gasesare main tained at a slight pressure Within the retort to insure thatthey penetrate and permeate the entire body of thecharge. The current ofreducing-gas is preferably, as shown, in an upward direction through theincandescent body of the charge. The rate of movement of the gas isregulated by the speed of the reaction, which can easily be determinedby an examination ot the gases discharged through `the ue E. The

operation is preferably continuous in character, additional quantitiesof the charge being introduced at the upper portion of the retort andthe metal tapped therefrom continuously or at intervals. I find thatthere is also produced, apparently as an intermediate product of thereaction, a coke-like substance, which is infusible at the temperatureemployed, but the nature of which has not been fully determined. Thissubstance contains both carbon and sulfur and may be a sulfocarbonate ofaluminium, a compound not heretofore known. Aluminium sulfid in a porouscondition is more easily reduced than any other readily-obtainablecompound of the metal, and the ease with which the sulfate is reducedaccording to my process may be explained by assuming that the sulfurcompound which is present serves to progressively convert the sulfateinto sullid and the colge-lik`e mass above referred to. This sulid isthen reduced by the sulfur-bearing hydrocarbon gas, such reduction beingfacilitated, as before stated, by the maintenance of a slight pressureof the reducing agent in excess of that of the atmosphere. It may befurther assumed that by the introduction of the carbon disulid with thehydrocarbon gas but a small proportion of aluminium sulid is `'nassepresent at any given period of the reaction and that the large excess ofinfusible sulfate maintains the mass in an open and permeable state. Thecoke-like product being infusible at the temperature employed aids inmaintaining the porosity of the charge.

The following reactions,whereby aluminium sulfate may be reduced tosulfid by carbon disultid, are established:

These reactions are introduced merely as indicating the probable courseof the reduction. In addition it is highly probable that other reactionsoccur and that aluminium oxid is present in small quantities.

As above stated, other compounds of aluminium may replace the sulfatewith corresponding variations in the reaction of reduc- If aluminiumoxid prepared in a porous 'condition by heating the sulfate be employed,

I find that under the influence of the described reducing agent itpasses readily into the coke-like mass above referred to and is thenreduced by the sulfur-bearing hydro-` carbon gas to metal, or if carbonin any form be present in admixture with the sulfate this same infusiblecokeflike mass is formed under the action of the sulfur-bearing reducingagent. The essential feature in all cases,what

ever be the character ot the raw material chosen for reduction, is thepresence in the reducing agent of sulfur in some form.

Certain modifications of the method will suggest themselves to thoseskilled rin the art. For instance, the reducing-gases may be heated toany desired temperature before introduction into the retort, theproportions of the reagents, as stated, may be widely de'- parted from,and the process may be applied to-the production of alloys of aluminium.

I claim- 1. The herein-described process of reducing an aluminiumcompound, which consists in subjecting such compound to the action of areducing agent of which sulfur is a component, at a temperaturesufficient to effect the reduction. c

2. The herein-described process of redlicing an aluminium compound,which consists in subjecting such compound to the action of a reducingagent consisting of a hydrocarbon gas containing sulfur, at atemperature suficient to eect reduction.

3. The herein-described process of reducing an aluminium compound, whichconsists in subjecting such compound, at a tempera- `ture sufficient toeffect the reduction, to a IOO IIO

ture sufficient to eect the reduction, to the action of a. reducing-gasof which snlfur is a component, and maintaining such gas at a pressurein excess of that of the atmosphere. 5 5. The herein-described processof reducing an aluminium compound, which consists in subjecting suchcompound ata, temperature sucent t0 eectthe reduction, to the action ofan upwardly-moving current of a. relo ducng-gas of which sulfuris a.component.

6. The herein-described process, which consists in subjecting porousaluminium sulfate, at a temperature suicient to eiect its reduction, t0the action of a. reducing agent of which sulfur is a component.

HEINRICH F. D. SCHWAHN.

Witnesses:

J. GEORGE HEID,v HY. G. OHEIM.

